检索结果-南通市图书馆

Temperature-controlled mode selection of Er-doped random fiber laser with disordered Bragg gratings

在线全文

学校读者我要写书评

暂无评论

Photonics research 2016年第3期4卷 102-105页

作者： W.L.zhang Y.B.Song X.P.zeng r.Ma z.J.Yang Y.J.rao Key Laboratory of Optical Fiber Sensing & Communications (Education Ministry of China) University of Electronic Science & Technology of China

In this paper, we proposed a way to realize an Er-doped random fiber laser(rFL) with a disordered fiber Bragg grating(FBG) array, as well as to control the lasing mode of the rFL by heating specific locations of the disordered FBG array. The disordered FBG array performs as both the gain medium and random distributed reflectors, which together with a tunable point reflector form the rFL. Coherent multi-mode random lasing is obtained with a threshold of between 7.5 and 10 mW and a power efficiency between 23% and 27% when the reflectivity of the point reflector changes from 4% to 50%. To control the lasing mode of random emission, a specific point of the disordered FBG array is heated so as to shift the wavelength of the FBG(s) at this point away from the other ***, different resonance cavities are formed, and the lasing mode can be controlled by changing the location of the heating point.

关键词： mode Temperature-controlled mode selection of Er-doped random fiber laser with disordered Bragg gratings

Demand-driven water withdrawals by Chinese industry： a multi-regional input-output analysis

在线全文

学校读者我要写书评

暂无评论

Frontiers of Earth Science 2016年第1期10卷 13-28页

作者： Bo zHANG z. M. CHEN L. zeng H. QIAO B. CHEN School of Management China University of Mining & Technology (Beijing) Beijing 100083 China State Key Laboratory of Coal resources and Safe Mining China University of Mining & Technology (Beijing) Beijing 100083 China School of Economics Renmin University of China Beijing 100872 China State Key Laboratory of Simulation and regulation of Water Cycle in river Basin China Institute of Water Resources and Hydropower Research Beijing 100038 China School of Management University of Chinese Academy of Sciences Beijing 100190 China State Key Joint Laboratory of Environmental Simulation and Pollution Control School of Environment Beijing Normal University Beijing 100875 China

With ever increasing water demands and the continuous intensification of water scarcity arising from China＇s industrialization, the country is struggling to harmonize its industrial development and water supply. This paper presents a systems analysis of water with- drawals by Chinese industry and investigates demand- driven industrial water uses embodied in final demand and interregional trade based on a multi-regional input-output model. In 2007, the Electric Power, Steam, and Hot Water Production and Supply sector ranks first in direct industrial water withdrawal （DWW）, and Construction has the largest embodied industrial water use （EWU）. Investment, consumption, and exports contribute to 34.6%, 33.3%, and 30.6% of the national total EWU, respectively. Specifically, 58.0%, 51.1%, 48.6%, 43.3%, and 37.5% of the regional EWUs respectively in Guangdong, Shanghai, zhejiang, Jiangsu, and Fujian are attributed to international exports. The total interregional import/export of embodied water is equivalent to about 40% of the national total DWW, of which 55.5% is associated with the DWWs of Electric Power, Steam, and Hot Water Production and Supply. Jiangsu is the biggest interregional exporter and deficit receiver of embodied water, in contrast to Guangdong as the biggest interregional importer and surplus receiver. Without implementing effective water- saving measures and adjusting industrial structures, the regional imbalance between water availability and water demand tends to intensify considering the water impact of domestic trade of industrial products. Steps taken to improve water use efficiency in production, and to enhance embodied water saving in consumption are both of great significance for supporting China＇s water policies.

关键词： water withdrawal embodied water use Chinese industry interregional trade multi-regional inputoutput analysis

A Cluster Dynamics Model for Accumulation of Helium in Tungsten under Helium Ions and Neutron Irradiation

在线全文

学校读者我要写书评

暂无评论

Communications in Computational Physics 2012年第5期11卷 1547-1568页

作者： Y.G.Li W.H.zhou r.H.Ning L.F.Huang z.zeng X.Ju Key Laboratory for Materials Physics Institute of Solid State PhysicsChinese Academy of SciencesHefei230031China Department of Physics University of Science and Technology BeijingBeijing 100083China

A cluster dynamics model based on rate theory has been developed to describe the accumulation and diffusion processes of helium in tungsten under helium implantation alone or synergistic irradiationwith neutron,by involving different types of objects,adopting up-to-date parameters and complex reaction processes as well as considering the diffusion process along with *** calculated results under different conditions are in good agreement with experiments much *** model describes the behavior of helium in tungsten within 2D space of defect type/size and depth on different ions incident conditions(energies and fluences)and material conditions(system temperature and existent sinks),by including the synergistic effect of helium-neutron irradiations and the influence of inherent sinks(dislocation lines and grain boundaries).The model,coded as IradMat,would be universally applicable to the evolution of defects for ions/neutron irradiated on plasma-facing materials.

关键词： Cluster dynamics model rate theory helium and neutron irradiation tungsten accumulation and diffusion

Effects of Current Stressing on Shear Properties of Sn-3.8Ag-0.7Cu Solder Joints

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2010年第8期26卷 737-742页

作者： X.J. Wang Q.L. zeng Q.S. zhu z.G. Wang J.K. Shang Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Department of Materials Science and Engineering University of Illinois at Urbana-Champaign Urbana IL 61801 USA

Effects of electromigration on microstructure, shear strength, and fracture behavior of solder joints were investigated by single-ball shear samples of eutectic Sn-3.8Ag-0.7Cu （SAC） joined by Cu plates at two sides. The electromigration tests were conducted at a current density of about 1.1×10^3 A/cm2 and a working temperature of about 83℃. The results showed that the shear strength and flow stress decreased greatly after current stressing. Such a decrease was associated with no significant loss of the fracture strain at short electromigration but a great reduction in the fracture strain after long-term current stressing. The variation of the fracture strain with the electromigration time was shown to result from the shift of the fracture surface from the center of the solder towards the intermetallic compound （IMC） interface at the cathode.

关键词： Strength Fracture strain Voids Solder

Influence of Solid Fraction on Gravity Segregation of Sn in A1-20Sn Alloy Casting

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2000年第6期16卷 577-580页

作者： zhang, P. Du, Y.H. zeng, D.B. Cui, J.z. Ba, L.M. Dep. of Mechanical Eng. Tsinghua Univ. Beijing 100084 China

The influence of solid fraction of Al-20Sn alloy mushy on gravity segregation of Sn in casting was studied . The relationship between solid fraction and the temperature of alloy mushy and that between solid fraction of alloy mushy and size of Sn particle in ingot were determined. The results show that the relationship between solid fraction and the temperature of alloy mushy was fs=1683-4.86t+0.003 5t2. The extent of gravity segregation of Sn in casting reduced gradually with the increase of solid fraction of alloy mushy. When solid fraction of alloy mushy was larger than 40%, the gravity segregation of Sn in casting could be removed basically, and the relationship between solid fraction of alloy mushy and size of Sn particle in ingot was s=-0.64fs+70.8.

关键词： Metal casting

Towards the diffusion source cost reduction for NdFeB grain boundary diffusion process

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2020年第1期36卷 50-54页

作者： H.X.zeng z.W.Liu J.S.zhang X.F.Liao H.Y.Yu School of Materials Science and Engineering South China University of TechnologyGuangzhou 510640China

Aiming at improving the performance/cost ratio in grain boundary diffusion process(GBDP),the critical rE containing Pr-Al-Cu alloy,less expensive rE containing La-Al-Cu alloy and non-rE Al-Cu alloy were employed as the diffusion *** preliminary results show that the coercivity was successfully enhanced from 1000 kA/m to 1695,1156 and 1125 kA/m by Pr70Al20Cu10,La70Al20Cu10 and Al75Cu25(at.%) alloys diffusion,respectively,due to the formation of(Nd,Pr)-Fe-B,La2 O3 and c-Nd2 O3 phases respectively,after *** is also found that the corrosion resistance can be improved by Al-Cu diffusion due to the positive effects of Al and Cu elements in grain *** present results demonstrated the various coercivity enhancement mechanisms for the GBDP based on different diffusion sources,and provided feasible solutions for cost reduction of GBDP and NdFeB production by saving rE resource.

关键词： Grain boundary diffusion Cost reduction Coercivity Microstructure Corrosion resistance

Mapping Sea Level rise Behavior in an Estuarine Delta System：A Case Study along the Shanghai Coast

在线全文

学校读者我要写书评

暂无评论

Engineering 2018年第1期4卷 156-163页

作者： H.Q. Cheng J.Y. Chen z.J. Chen r.L. ruan G.Q. Xu G. zeng J.r. zhu z.J. Dai X.Y. Chen S.H. Gu X.L. zhang H.M. Wang State Key Laboratory of Estuarine and Coastal research East China Normal University Shanghai 200062 China Shanghai Water Planning Design and research Institute Shanghai 200232 China Shanghai Water Authority Shanghai 200050 China School of Urban and regional Science East China Normal University Shanghai 200062 China School of Ecological and Environmental Sciences East China Normal University Shanghai 200062 China Shanghai Hydrological Station Shanghai 200232 China Shanghai Municipal Bureau of Urban Planning and Land resources Shanghai 200003 China Shanghai Institute of Geological Survey Shanghai 200072 China

Sea level rise （SLr） is a major projected threat of climate change that is expected to affect developing coastal cities located in estuarine delta regions, Shanghai is one such city, being located in the Yangtze river Delta （YrD）, It is difficult, however, for decision-makers to implement adaptation due to the uncer- tain causes, magnitudes, and timings of SLr behaviors, This paper attempts to map the causes and mag- nitudes of SLr behaviors on a decadal scale, We analyze the tidal level records from 11 tidal gauge stations and the corresponding bathymetry measurements around these stations since 1921, We identify three new SLr behaviors along the Shanghai coast due to anthropogenic geomorphologic changes （AGCs）, besides the well-known eustatic sea level rise （ESLr）, tectonic subsidence （TS）, and urban land subsidence （ULS）, The first new behavior is regional sea level rise （rSLr）, which occurs as a result of land reclamation and deep waterway regulation, The second is regional sea level fall （rSLF）, which occurs because the channel bed is eroded due to sediment supply decline in the river catchment, The last SLr behavior is local tidal datum rise （LTDr）. Thus, we project that the magnitude of SLr for the Shanghai coast ranges from 10 cm to 16 cm from 2011 to 2030, Clarifying SLr behaviors is important to aid local decision- makers in planning structural and non-structural measures to combat escalating flood damage costs in an estuarine delta system; this field is full of future challenges,

关键词： Sea level rise behavior Anthropogenic geomorphologic change Local tidal datum Flood management Adaptation

Transparent flexible znO/MWCNTs/PBMA ternary nanocomposite film with enhanced mechanical properties

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Chemistry 2016年第8期59卷 1010-1017页

作者： Xingwei Han Xiaofei zeng Jiexin Wang Dejia Kong N.r. Foster Jianfeng Chen State Key Laboratory of Organic-Inorganic Composites Beijing University of Chemical Technology Beijing 100029 China Department of Chemical Engineering Columbia University New York 10027 USA Supercritical Fluids research Group School of Chemical Engineering University of New South Wales Sydney New South Wales 2052 Australia research Center of the Ministry of Education for High Gravity Engineering and Technology Beijing University of Chemical Technology Beijing 100029 China

Functional organic-inorganic nanocomposites with high transparency show significant potential application in many fields. However, it is still a great challenge to prepare flexible transparent nanocomposites due to the intrinsic stiffness of the nanoparticles and the poor interaction between nanopartieles and organic matrices. In this work, a transparent ternary nanocomposite film with enhanced mechanical performance is fabricated by two-steps. First, the transparent ternary znO/MWCNTs/n-butyl methacrylate （BMA） nanodispersion is prepared by mixing the znO/BMA and MWCNTs/BMA dispersions directly. Then, the ternary nanocoposites film is fabricated via in-situ bulk polymerization of the above nanodispersions. As a result, the tensile strength of the znO/MWCNTs/poly-n-butyl methacrylate （PBMA） ternary film is enhanced by 42% and the elongation at break is three times that of znO/PBMA nanocomposite. The hardness of the film increases from 5B to 1H with 40 wt% znO. These results indicate that znO and MWCNTs can improve the mechanical properties of the composite significantly. Importantly, the ternary nanocomposite film still remains high transparency and exhibit excellent UV-shielding performance. The as-prepared transparent multifunctional nanocomposite films have promising applications in optical materials and devices, such as optical filters, contact lenses and protection packing.

关键词： znO carbon nanotubes transparent ternary nanocomposite UV-shielding mechanical properties

redesign of the gStore system

在线全文

学校读者我要写书评

暂无评论

Frontiers of Computer Science 2018年第4期12卷 623-641页

作者： Li zeng Lei zOU School of Electronics Engineering and Computer Science Peking University Beijing 100871 China Beijing Institute of Big Data research Beijing 100871 China

gStore is an open-source native resource Description Framework （rDF） triple store that answers SPArQL queries by subgraph matching over rDF graphs. However, there are some deficiencies in the original system design, such as answering simple queries （including one-triple pattern queries）. To improve the efficiency of the system, we reconsider the system design in this paper. Specifically, we propose a new query plan generation module that generates different query plans according to the structures of query graphs. Furthermore, we re-design our vertex encoding strategy to achieve more pruning power and a new multi-join algorithm to speed up the subgraph matching process. Extensive experiments on synthetic and real rDF datasets show that our method outperforms the state-of-the-art algorithms significantly.

关键词： graph database subgraph matching rDF management SPArQL query